In order to investigate the unsteady performance of a propeller-rudder system,the integral solution method was adopted for prediction purposes.The interaction between propeller and rudder was considered by recalculating influence coefficients,and both were solved at the same time.The calculation model was consummated by predigesting complex rulers of influence coefficients.A propeller called HSP produced by the propulsion committee of the 22nd ITTC was used to validate the veracity of the program.Influence of propeller wake on the rudder was studied,and the propulsion performance of a propeller and rudder system was calculated in steady flow.The mean value of computation of unsteady flow was compared with that of the steady flow.Comparison results indicate that it is feasible to use the integral solution method for predicting the unsteady performance of a propulsion system.